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Old 3rd Oct 2022, 6:26 am   #21
Retrorepair
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Default Re: Sony KV-A2942U very soft focus in middle of screen

I really had no idea the grille could bow on these, but I suppose anythings possible!

Could that explain the difference in distance between the beams from middle to edge? I'd assume not as surely the grill only masks the bleed amd doesn't actually deflect anything?

I'll work through the manuals steps anyway and either post the outcome here or let you know where I'm getting confused, I do appreciate the help.

I think the main things that confuse me are:

A: The difference between purity, V STAT and hexapole
B: The diagrams show RGB and arrows below pointing to a dot, is this saying turning in one direction makes them flip? Since the opposite seems to be BGR?

Also do I move both tabs in unison or separately? It's not really clear in the manual.

It's that extreme difference in separation I'm mostly concerned about. If the center is perfect, the rest of the screen seems totally wacky no matter what I do. I'll start from scratch anyway and see how I go.
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Old 3rd Oct 2022, 9:09 am   #22
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Default Re: Sony KV-A2942U very soft focus in middle of screen

The static convergence is OK and only this, as the service manual states, is adjusted by the ring magnets fixed to the neck of the CRT.

You need to follow the Sony Service Manual instructions for dynamic convergence which is very similar to PIL CRT instructions.

Unless seen otherwise, purity seems OK.

With the screen viewed by a mirror, leaning over the set will not do, remove the rubber bungs etc and using gloves, move the scan coils about their axis and you will soon get the hang of it. Just remember in the Sony factory staff not robots did this every day.

I appreciate the comment that a BVM monitor is on a different planet to a domestic receiver and dynamic focus does work very well but until the convergence is correct, you will not get anywhere.

Good luck

Chris
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Old 3rd Oct 2022, 12:52 pm   #23
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Default Re: Sony KV-A2942U very soft focus in middle of screen

So I'm just moving the yoke back and forth and tilting? I don't get how to do that with the rings still on and it mentions to remove the spacer, what is that?

I feel like if I watched someone do it everything would click but I've got a mental block at the moment understanding what is meant by some of this.
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Old 3rd Oct 2022, 1:49 pm   #24
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Default Re: Sony KV-A2942U very soft focus in middle of screen

Had a look round and think I get it now, yes the entire yoke needs to be reset I think. I believe that extreme separation on the edges and the slight bowing can be solved by that. Great, once my chassis is 100% dry (cleaned it up yesterday, will give it a final blast of the hair dryer today after 24 hours in the hot airing cupboard) I'll get it back together and see if I can't finish this off.
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Old 3rd Oct 2022, 3:21 pm   #25
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Default Re: Sony KV-A2942U very soft focus in middle of screen

No, no, no. Not back and forth just the axis. Back and forth will affect purity and is covered in the service manual as such.

Up and down, left and right after removing the bungs.

Have a look at "Sony Trinitron TV Color Purity & Convergence repairs" on YouTube which will walk you through the adjustment and illustrate the changes when making them on a domestic Sony.

Chris
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Old 3rd Oct 2022, 10:31 pm   #26
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Default Re: Sony KV-A2942U very soft focus in middle of screen

Hi.
Indeed there is only one way or these days two!! Hands on or youtube. I'd do a video and put it on my channel but I don't have a Triniton CRT set these days. The problem with the manual is that it's written for engineers not someone that is unfamiliar with the technology. Follow the previous advice and you'll get there.
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Old 4th Oct 2022, 7:24 am   #27
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Default Re: Sony KV-A2942U very soft focus in middle of screen

Gotcha. The manual literally makes it look like (to me anyway) you need to move back and forth.

Well I had a crack last night and I think the act of moving the chassis out and putting it back in has made the flybacks "fizzing" worse. I felt a tingle as I was going to move the chassis and realised it was the HT cable. I then noticed visible arcing at the top of the flyback so think it's time to replace it before I go any further. It does look as if there has been arcing there for a while as it looks a little burned on top so guess there's a crack under the rubber cap.

I did try to focus anyway since it was making this noise before to no real ill effect but literally when it gets close to good focus, the tube neck audibly rings like a fire bell!

I'll get a replacement and report back.

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Old 4th Oct 2022, 6:43 pm   #28
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Default Re: Sony KV-A2942U very soft focus in middle of screen

I had quite a few Grundig TVs through my hands that had been badly "smoked up". I once had a hybrid where the blue tripler had big "holes" in it, probably to prevent tracking across.That TV was so bad that the "holes" in the tripler were solid with cigarette tar.
So I used to wash in hot water and a detergent (something called "Zoom".
After much washing clear with hot water only, I would take it out, still hot from the sink, and hang it up in my boiler house. I would just leave it there for at least a week.
I NEVER had a problem related to the practice.
I have converged many TVs, from G8 onwards, but later spent a couple of years setting up radom CRTs, often changing yokes.
We had a trinitron CRT one day, but I had no suitable chassis in which to test it. What I did do is have a good look at all the stuff attached to the glass, obviously for convergeance. Plastic sticks with a bit of magnetic plastic stuck just about everywhere. I imagine those Sony operatives who did the settings took a while to train to proficiency!
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Old 5th Oct 2022, 8:55 am   #29
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Default Re: Sony KV-A2942U very soft focus in middle of screen

I'm a bit concerned about the pinging noise in the tube neck. Hopefully it will go away.

I've never had this on a Trinitron, but the old 45AX tubes used to do this frequently. The solution (i.e. bodge) was to slightly increase the heater voltage, but that's not something I'd ever do on a Sony.

It's worth havig a look under the rubber cap. Some Sony LOPTs had the wire as a bayonet or maybe push fit, which might save you the trouble and expense of locating a new transformer. Otherwise epoxy filler is a good way to go - you've nothing to lose.
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Old 5th Oct 2022, 3:38 pm   #30
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Default Re: Sony KV-A2942U very soft focus in middle of screen

I actually put a bit of dielectric grease around the opening of the HT cable and popped the rubber cap back over, seems to have solved it for now. I may 3d print a 4 part assembly to encase it since PLA has some pretty impressive insulating properties, at least when printed with 100% infill at the right thickness.

I've also made some dynamic convergence adjustments which I think have solved moat of the convergence and bowing issues.. and created a new one at the very bottom where it bows out at the sides. The service menu adjustments don't help so I guess I'll be trying again. What a pain it was though!
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Old 5th Oct 2022, 3:41 pm   #31
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Default Re: Sony KV-A2942U very soft focus in middle of screen

Oh, the "alarm bell" ringing on the neck seems to have gone too
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Old 5th Oct 2022, 3:48 pm   #32
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Default Re: Sony KV-A2942U very soft focus in middle of screen

I may replace the FBT down the road anyway, if it makes no difference, at least I'll have a spare. I'm starting to think the grille may be warped though which is a shame. Just need to find another AE2 era tube. Easier said than done I think!
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Old 5th Oct 2022, 11:23 pm   #33
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Default Re: Sony KV-A2942U very soft focus in middle of screen

Service menu to the rescue!

It's so easy to stay in the box, but geometry requires you to think outside of it. Or at least, think in more than 2 dimensions.

I pushed the lower pin further out and made the top match to the point the whole image was pinned, then used the main pin cushion control to balance the lot out.

I think I'm done with this thing. As mentioned on page 1, this isn't a PVM/BVM and even then, perfection is impossible on these consumer sets and really, that's most of the reason I love them.

Thank you all for your help guys!
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Old 6th Oct 2022, 8:46 am   #34
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Default Re: Sony KV-A2942U very soft focus in middle of screen

I had numbers of Sony receivers that had received a heavy bump that caused mainly rainbow mis convergence and focus problems.
I think the very heavy weight of the large screen models lead to them being dropped by their owners. The 27" models were heavy but nothing like the 29" ones that almost without exception had flat tubes. I could never work out why the 29" ones were so heavy other than very thick glass. J.
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Old 6th Oct 2022, 8:59 am   #35
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Default Re: Sony KV-A2942U very soft focus in middle of screen

Hi.
The Sony wide screen Triniton tubes were by far the worst with short lives and misregistration, they went low emission very quickly, by that time I had left Sony (SES Glasgow) and ran my own business, I left Sony when the AE2B chassis was current.
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Old 6th Oct 2022, 9:02 am   #36
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Default Re: Sony KV-A2942U very soft focus in middle of screen

Sony were very quick to incorporate their experience in the design of professional monitors to their domestic receivers particularly for the US market.

Comb filters, 10Mhz video response IC video output. CRT based video output long before they were adopted by others. Specialist geometry IC to match the Trinitron CRT design, fine pitch aperture grill which really did make a difference, velocity modulation, computer CRT yoke design and so on.

In many ways the limiting factor was the broadcast system. Whilst DVD and later Blue Ray made a vast difference, squeezing extra information out of a system designed for 4:3 picture ratio then stretched to 16:9 was a tough nut to crack.

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Old 6th Oct 2022, 9:10 am   #37
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Default Re: Sony KV-A2942U very soft focus in middle of screen

Trinitrons of course always had more glass than other sets but earlier models usually had metal cages also which didn't help matters.

This A2942U weighs 35kg but as you say, has a nearly flat tube. Absolutely beautiful piece of furniture though.
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Old 6th Oct 2022, 9:18 am   #38
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Default Re: Sony KV-A2942U very soft focus in middle of screen

I dont think scan velocity modulation (SCAVEM) was a Sony innovation, I think it was from Philips more or less at the same time as Colour Transient improvement (CTI) to improve the apparent sharpness of strong luminance and chrominance transients.
Both very impressive on a pattern but not so much on live pictures.
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Old 6th Oct 2022, 12:03 pm   #39
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Default Re: Sony KV-A2942U very soft focus in middle of screen

Hi Marcel

You make a good point.

I can't remember if CTI was switchable in UK sets. I believe it was introduced to compensate for the characteristics of the 5.5Mhz video bandwidth found in Europe whilst the BBC used 6 Mhz to improve the chrominance slope.

VM was switchable and I did switch it off, or maybe unplugged the lead. Apart from watching cartoons it wasn't really my cup of tea.

I know that my Sony KV2000 gives an outstanding picture with colour bar edge definition as sharp as my monitor and a video frequency response as equal to a Philips G11 but whose luminance edge definition is nowhere near as good.

My KV2204 however, with ceramic filters to shape it all, is not in the same league.

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Old 6th Oct 2022, 3:46 pm   #40
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Default Re: Sony KV-A2942U very soft focus in middle of screen

Quote:
Originally Posted by simpsons View Post
I can't remember if CTI was switchable in UK sets. I believe it was introduced to compensate for the characteristics of the 5.5Mhz video bandwidth found in Europe whilst the BBC used 6 Mhz to improve the chrominance slope.
Chris
Hi Chris,
I think CTI was also useful in the I system as even with 0,5 MHz more video bandwidth the choma BW is sill about 1/4 of the luma BW.
But it's in SECAM that the improvement was the most impressive (on a colour bar pattern) because of the very bad transient response between saturated colours due to the effrect of the deemphasis on the truncated maximum frequency deviation and amplitude.
But even then it did not make much difference on real pictures.
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